1. Field of the Invention
The present invention relates to a heat control method and a heat controller, and more particularly to a heat control method and heat control apparatus suitable for use in heat control of heat generated by electronic equipment mounted aboard a space vehicle including a man-made satellite and a spaceship.
2. Related Art
In general, in a space vehicle traveling through a vacuum environment, radiation of heat into space via the outer skin of the space vehicle serves as a means of heat regulation for the space vehicle.
For this reason, many techniques have been developed to prevent a great increase or a great decrease in temperature and for maintaining the temperature within an appropriate range when there are large changes in the amount of internally generated heat within the space vehicle.
For example, the approach of providing a temperature-control circuit separate from the electronic equipment, and that of using a thermal louver system, such as shown in FIG. 6 of the Japanese unexamined patent publication (KOKAI) No.11-217562 are known.
The provision of a separate temperature-control circuit, however, not only increases the mass of the space vehicle and the amount of energy consumed, but also leads to an inevitable increase in the internal volume of the space vehicle, and increases the number of moving parts used therein, which leads to problems of low reliability and lifetime.
In Japanese patent No. 2705657, there is shown a method whereby a phase-transition substance is provided between a stable heat source within a man-made satellite and a component of the man-made satellite having a heat radiating surface exhibiting great thermal variations, wherein temperature control is performed, the phase-transition substance having a small thermal conductivity at a high temperature and a large thermal conductivity at a low temperature.
However, the above-noted constitution with regard to thermal conductivity at a low-temperature phase and thermal conductivity at a high-temperature phase is the reverse of the constitution of the present invention, to be described below, making efficient temperature control impossible.
In Japanese patent No. 2588633, there is disclosure of a temperature controller for electronic equipment in a space vehicle, this being formed by a vessel into which a phase-change substance is sealed, a heat pip in intimate contact with the vessel, and an electric heater in intimate contact with an outer surface of the vessel. However, because additional equipment requiring a separate heater increases in weight, this is not suitable for use in a space vehicle.
Additionally, in Japan patent 2625821, there is disclosure of a heat controller for a man-made satellite, in which a phase-transition substance having a low infrared radiation efficiency at a high-temperature phase, and having a high infrared radiation efficiency at a low-temperature phase is disposed between a piece of payload equipment temperature control and a heat sink. However, the constitution in this heat controller with respect to the infrared radiation efficiencies at low- and high-temperature phases is the reverse of that in the present invention, described below, and it is impossible to perform efficient temperature control.
In the Japanese unexamined patent publication (KOKAI) No.63-207799, a configuration in which a single phase-change substance made of vanadium dioxide is disposed between a piece of payload equipment and a heat sink. However, this uses a different phase-change substance than the present invention, which is described below, the method of use thereof is also different, and it does not enable efficient temperature control.
In the Japanese unexamined patent publication (KOKAI) No.11-217562, as shown in FIG. 2, there is a proposal of, rather than relying on a mechanical principal, simply using the heat radiation characteristics of a phase-change substance made of perovskite Mn oxide or the like, used in the heat controller to control the temperature.
Specifically, the example shown is one in which a phase-change substance 1 is directly attached to a heat radiating surface 5 of the object 3, which is a piece of electronic equipment requiring heat control.
In the above-noted examples of known technology, however, the phase-change substance used is one type, perovskite Mn oxide or the like, so that at high temperatures the heat radiation efficiency is high and at low temperatures the heat radiation efficiency is low.
In a heat controller using the above-noted known phase-change substance, because it is necessary to achieve a high radiation efficiency with the phase-change substance alone at a high-temperature phase, it was necessary to have a thickness of several hundred microns.
In the case of using perovskite Mn oxide as a phase-change substance, because of the high density (6.6 g/cm3) of this substance, at a thickness of 200 μm, for example, the weight of the required amount of material would be as much as 1.3 kg/m2.
Furthermore, because this phase-change substance is a ceramic material and having hard condition, it has the drawback of making it impossible to achieve a phase-change substance that is both thin and flexible.
Although this phase-change substance has only ⅓ to ⅕ the mass of a thermal louver having the same function and which is opened and closed by a blade or bi-metal element having the same function, this is still insufficient to meet the stringent weight requirements of a space vehicle, and there is a need for even further reduction in mass.
Additionally, because the phase-change substance is a solid and does not exhibit flexibility, it is difficult to mount it to an object having a curvature, thereby limiting its scope of application.
The shape of a space vehicle includes curved surfaces, and if mounting were possible to these surfaces, there would be a further enhancement in the range of applicability. However, as long as use is limited to a single layer of the above-noted phase-change substance of the past, it was difficult to achieve a practical heat controller in the past.
Accordingly, it is an object of the present invention to improve on the above-noted drawbacks of the prior art, by providing a heat controller and a method for controlling heat, which is lighter and higher in performance than a heat controller having equivalent heat radiation characteristics in the past.
It is a further object of the present invention to provide a heat controller wherein a phase-change substance, which in the past needed to have a thickness of several hundred microns or more, is formed as a film having a thickness of approximately several microns on a low-density base material, and which has heat radiation characteristics equivalent to a heat controller in the past.
It is yet another object of the present invention to provide a heat control and a method for controlling heat in which flexibility is imparted so as to enable application to an object having curvature.